There is a system using an electric field coupling method as a power transmission system. The power transmission system transmits electric power to a power receiving device from a power transmitting device when active electrodes of the power transmitting device and the power receiving device oppose each other and a strong electric field is formed between the two electrodes to establish electric field coupling between the electrodes.
International Publication No. 2013/054800 pamphlet discloses a power transmission system using the electric field coupling method. The power transmission system as disclosed in International Publication No. 2013/054800 pamphlet stabilizes a reference potential of a power receiving device in power transmission to the power receiving device from a power transmitting device and causes no malfunction in the power receiving device. In the power transmission system, both the power transmitting device and the power receiving device include a reference potential electrode connected to a reference potential. The reference potential electrodes are made to oppose each other when power is transmitted to the power receiving device from the power transmitting device so as to stabilize the reference potential of the power receiving device and stabilize operations of the power receiving device.